Mercury drops by 14°C, scattered showers today

Intense showers on Wednesday evening ended a six-monthlong dry spell leaving interior roads flooded and holding up peak-hour traffic. The meteorological office has forecast thundershower towards the afternoon or evening on Thursday.

At noon on Wednesday, the temperature peaked to a maximum of 39°C, the second highest this year so far. Sea breeze entered the city and brought the temperature down by 5°C in about 40 minutes. The temperature fell further by nearly 10°C to 25°C by 3pm when the downpour began.

“Storms originated around Tiruttani (Tiruvallur district) and moved in south-eastwards towards the city. After bringing rain in Chennai, the storm moved further towards Mahabalipuram,” former deputy director general of Regional Meteorological Centre Y E A Raj said.

Rain in the city was a result of convective activity. According to weathermen, most parts of Tamil Nadu get rainfall when the southwest monsoon is inactive in other parts of the country as the state falls in the rain shadow region. Westerly winds weaken when the southwest monsoon is inactive giving way to easterly winds. Easterlies bring in enough moisture which is pushed skywards by the heat built up during the day to form rain clouds.

On Wednesday, Nungambakkam recorded nearly 3cm rainfall from an intense shower that lasted about 20 minutes around 3pm. The rest of the evening it drizzled across the city. The evening showers brought 5cm rainfall at Taramani, 4cm at Kelambakkam, 2cm at Meenambakkam, 3.6cm at Sholinganallur and 3.4cm at Puzhal.

The southwest monsoon, which set in over Kerala last week, is yet to gather steam. Some parts of the southern peninsula recorded light to moderate rainfall in the 24 hours until 8.30 am on Wednesday. Jayamkondam (Ariyalur district) and Gingee (Villupuram district) received 3cm each, Chidambaram (Cuddalore district), Salem (Salem district), Neyveli AWS (Cuddalore district), Thanjavur (Thanjavur district), Karaikal (Karaikal district) and Mettur (Salem district) received 2cm rainfall each.